The present invention relates to a method of producing a gas barrier layer by using plasma-enhanced CVD. More specifically, the invention relates to a gas barrier layer production method capable of depositing a gas barrier layer having not only excellent gas barrier properties but also excellent oxidation resistance and high transparency.
A gas barrier layer (a water-vapor barrier layer) is formed not only on sites or parts requiring moisture resistance in various devices including optical devices, display devices (e.g. liquid-crystal displays and organic EL displays), semiconductor devices and thin-film solar batteries, but also in packaging materials used to package food, clothing, electronic components, etc.
Layers made of various materials such as silicon oxide, silicon oxynitride and aluminum oxide are known gas barrier layers. A gas barrier layer made of silicon nitride is known as one of those layers. Plasma-enhanced CVD is a known method of producing a gas barrier layer made of silicon nitride.
For example, US 2008/0211066 A1 describes a gas barrier layer production method in which a gas barrier layer made of silicon nitride is formed on a substrate surface by plasma-enhanced CVD using silane gas, ammonia gas and a carrier gas, wherein two or more silicon nitride sublayers having different Si/N composition ratios are deposited by maintaining the substrate temperature at 200° C. or less and adjusting the flow rate ratio of the ammonia gas to the silane gas.
The production method described in US 2008/0211066 A1 is capable of obtaining a gas barrier layer which exhibits high oxidation resistance in a high temperature and high humidity environment, has few pinholes and exhibits high transparency (optical transmittance).